INT 01H: Single-Step Interrupt

 When the CPU Trap Flag is set (TF=1), the CPU executes this interrupt
 after each instruction.

 Debuggers which allow you to single-step through the instructions of a
 program use this interrupt to recapture execution to display the
 registers, memory, etc.

 Trapping is turned off (TF=0) upon execution of any INT instruction, so
 the INT 01H itself is not executed in single-step fashion.  Upon leaving
 the interrupt (via IRET), all flags are restored, thus the next
 instruction will be trapped.

 The normal way to begin single-stepping is to PUSH a word containing all
 the desired flags (including TF=1), PUSH the desired CS and IP address to
 execute, then perform an IRET to begin single-stepping at that address.

See Also: INT 03H
          ROM-BIOS Functions
          DOS Functions
          Process Control Functions
                                    -♦-